scsi: Conditionally compile in constants.c

Instead of having constants.c littered with ifdef statements we should
be moving dummy functions into the header and condintionally compile in
constants.c if selected. And update the Kconfig description to reflect
the actual size difference.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Tested-by: Robert Elliott <elliott@hp.com>
Reviewed-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 9c92f41..b021bcb 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -201,12 +201,12 @@
 	  certain enclosure conditions to be reported and is not required.
 
 config SCSI_CONSTANTS
-	bool "Verbose SCSI error reporting (kernel size +=12K)"
+	bool "Verbose SCSI error reporting (kernel size +=75K)"
 	depends on SCSI
 	help
 	  The error messages regarding your SCSI hardware will be easier to
 	  understand if you say Y here; it will enlarge your kernel by about
-	  12 KB. If in doubt, say Y.
+	  75 KB. If in doubt, say Y.
 
 config SCSI_LOGGING
 	bool "SCSI logging facility"